Visual demonstrator



June 10, 1941. w, M c cc o 2,245,110

VISUAL DEMONSTRATOR Filed Jan. 24, 1940 2 Sheets-Sheet 1 ATTORNEYS June 10, 1941. w, M cc 0 2,245,110

VISUAL DEMONSTRATOR Filed Jan. 24, 1940 2 Sheets-Sheet 2 'll my I NNNNN OR Patented June 19, 194:1

VISUAL DEMON STRATOR William Marcaccio, West Covington, Ky. Application January 24, 1940, Serial No. 315,415

6 Claims.

This invention relates to means for visually illustrating varying magnetic flux and in its particular preferred embodiment to a novel device for graphically depicting internal structure'of an electric motor of the induction type and the play of magnetic flux about motor parts during operation.

A broad general object of this invention is to provide means for illustrating by inter-related and synchronized variations in light intensity transmitted by means of any well known projecting apparatus through localized areas of a nonopaque screen,- the continuous uniform change by imperceptible stages produced in the magnetic flux of a magnet by other magnetic forces moving in its vicinity.

In a more limited sense, it is an object of this invention to provide a visual demonstrator of an induction type electric motor illustrating the coordination of the parts thereof and the play of magnetic flux thereabout occurring during operation of the motor.

It is another object of this invention to provide a visual demonstrator of an electric motor of the induction type wherein is graphically shown in appropriate synchronism the growth and collapse of magnetic flux at each polepiece of the motor during its operation.

A still further object of this invention is to provide a device suited to being interposed in the path of the be m of a projection machine for producing a projected dynamic image showmotor of the induction type during operation,

An advantageinherent in the novel device according to this invention, principally important from the standpoint of manufacture, is that the device comprises a series of superposed fiat ele-' ments connected by pins whereby the elements of the device can be fabricated by simple stamp- Regarded in certain of its broader aspects, the

novel demonstrator according to the present invention for illustrating variations in magnetic flux in an electro-magnetic device comprises a front screen carrying indicia corresponding to elements of the device the operation of which is to be demonstrated, transparent areas in said screen corresponding to localities of the device wherein during operation magnetic flux plays, a first set of polarizers arranged to intercept light rays in a common plane relatively fixedly mount- I ing flux changes in internal parts of an electric ing operations suiting the device to manufacto'the present invention will be apparent to those skilled in this art during the course of the following description.

ed across said transparent areas, and a second set of polarizers moving in correlated synchronism behind said first set of polarizers whereby the intensity of light transmitted through said first and second sets of polarizers is relatedto the intensity of magnetic flux of the corresponding element of the device being illustrated.

In order to facilitate a fuller and more complete understanding of the present invention a specific embodiment thereof herein illustrated will be hereinafter described, it being clearly understood, however, that the illustrated embodiment, although presently preferred, is provided .solely'by way ,of example of the practice of this invention and'not by way of-limitation thereof except insofar as the invention is recited in the subjoined claims.

Referring then to the drawings,

Figure 1 is substantially a front elevational view of the presently preferred embodiment of this invention,

Fig. 2 is substantially a rear view of the device illustrated in Fig. 1,

Fig. 3 is an enlarged view of internal parts of the device illustrated in the foregoing figures,

Fig. 4 is substantially a plan view of the front masking plate,

Fig. 5 is essentially a vertical sectional view of Fig. 4 taken along the line 5-5 thereof,

Fig. 6 is substantially a vertical sectional view of Fig, 2, taken along the line 66 thereof, and

Figs. 7 to 10 inclusive illustrate relationships of moving parts of the device during successive steps in its operation.

As will be obvious from an inspection of the drawings the herein illustrated presently pre-' ferred embodiment of this invention comprises a supporting standard 20 having a threaded end portion 2| for receiving a nut 22 by which a bent marginal part 23a'of a screen 23 can be attached to the standard and supported thereon in up right position substantially as shown.

The screen 23 has formed therein a centrally located "substantially circular opening 231) behind which is mounted in registry therewith a disc 24 of transparent sheet material spaced with respect to the screen by an annulus 25 and held in fixed relationship by screws 28 passing through openings 260 formed in the disc 24 whereby the assembly is substantially as shown in Fig. 6'. The disc 24, although intrinsically transparent, is coated with opaque material to define upon the surface thereof a plurality of visually distinct areas whereby projection of an image on the sheet can be accomplished by transmitting the beam of a projection apparatus therethrough. There are however provided upon the sheet several areas of unimpaired transparency, notably those designated by the reference character 24a in Fig. 4. These transparent areas are intended to simulate in relation and substantially in shape elements of an induction motor and, as will be apparent from the drawings, correspond to the armature and polepieces thereof.

Within the transparent areas corresponding to the polepieces are mounted slips 21 of sheet polarizing-material such as the substance commonly sold under the trade name Polaroid which possesses the property of extinguishing light rays vibrating in one direction while substantially transmitting, except for losses due to absorption, light rays vibrating in a direction perpendicular to the first direction of vibration. These polarizing slips 21 are arranged upon the transparent disc 24 in a manner such that they each polarize light vibrating in a common plane.

. A series of opaque indicia 21a are provided across the polarizing slips 2! for the purpose of diagrammatically illustrating windings of the polepieces.

A plurality of peripherally toothed transparent discs 28, 29, 38 and 3| arranged in a common plane with their centers lying within a circle and equally angularlyspaced with respect each to the other are freely rotatably supported upon pivots 28a, 29a, 38a and 3|a respectively which are mounted in supporting elements 28b, 29b, 38b and 3|b respectively attached to openings 28a, 29a, 38a and 3|a' in the disc 24. Spacer elements 280, 29c, 38c and 3|c are provided on the pivots 28a, 29a, 38a and 3|a respectively to prevent rubbing of the discs 28,

29, 38 and 3| against the disc 24 or against the supporting annulus 32 which, positioned behind the discs 28, 29, 38 and 3|, serves the better to support the assembly firmly in position.

A peripherally toothed transparent disc 33 freely rotatably mounted upon a pin 33a is positioned in a plane common with the plane of the discs 28, 29, 38 and 3| in a manner such that its teeth engage with the teeth of each of said discs. An opaque area 33d provided upon the disc 33 serves to simulate a portion of the armature of an induction motor.

The discs 28, 29, 38 and 3| each'carry fixedly secured thereto sheet polarizing ,material 2811, 2911,3811 and 3|d respectively. Contrasted to the disposition of the polarizing slips 21 hereinbefore described, the polarizers 29d, 29d, 38d and 3|d are not disposed in a manner such as to extinguish light vibrating in a common plane but in stead are disposed in a manner such that the angle of vibration extinction of each disc diifers from the disc preceding it, moving in a clockwise direction, by an angle of 45 so that discs diametrically opposite each other would, if superposed, glve complete extinction of transmitted light within the limitations of the polarizing 1 I media.

* means 36 in a manner such that disengagement of the annulus from the disc edge portions is substantially precluded. As will be obvious, rotation of the annulus will result in rotation of each of the discs in a corresponding direction and rotation of the centrally located disc 33 in an opposite direction.

The polarizers and masking screen 24 herein- I Having thus described the structural features I of the novel demonstrator device according to the preferred embodiment of this invention, its mode of operation now will be described, reference being made particularly to Figs. '7 to 10 inclusive. It is to be assumed that in each instance the polarizer extinctionplane is parallel to the field lines drawn across the slips 2'! and the discs 28, 29, 38 and 3|. In Fig. '7 it will be noticed that the disc 3|' is set at full extinction position with respect to the corresponding polarizer slip 2'! and that the disc 29 is set at full transmission position, whereas the discs 28 and 38 are set at intermediate positions. This results in transmission of light through the topmost slip 21 and extinction of transmitted light termediate slips. it will be noted that the opaque area 33d on the in the lowermost slip 21 whereas partial extinction is observed in light transmitted in the in- With the discs so positioned disc 33 is positioned nearest the topmostdisc 29, or in other words, maximum light transmission occurs through the disc nearest the opaque area 33d. This corresponds to maximum magnetic flux and in like manner intermediate degrees of magnetic flux intensity find their corresponding value in the intensity of light transmitted through the intermediate discs 28 and 38, whereas the minimum flux finds its counterpart in the extinguished transmitted light obstructed by the crossed polarizers 3| and the lowermost slip 21.

Referring now to Fig. 8, the positions occupied by the several discs 28, 29,- 38 and 3| and 33 is illustrated after the internally toothed gear 34 has been rotated ina counter-clockwise direction to cause movement of the opaque portions 33d on the disc '33 to a position near the polarizing disc 33. With the discs so positioned transmitted light passes freely through the disc 38 but is completely extinguished by the disc 28 which is set at right angles to the extinction angle of the polarizer slips 21 and transmitted light of intermediate intensity passes through the discs 29 and through the disc 33 is substantially completely extinguished and light of intermediate intensity is transmitted through the discs 29 and 3|.

As will be obvious to those familiar with phenomena associated with polarized light, the rotation of the polarizers results in continuous uniform and gradual extinction of light as the polarizers are moved into position at right angles to each other. The extinction does not occur stepwise in the sense that the steps may be visually perceived, but each step appears to blend so completely with the preceding and succeeding step as to defy drawing of a line of demarkation between the steps by mere inspection of the projected image. This variation in light intensity corresponds in character to the variation in magnetic fiux intensity when magnetic objects are moved with respect to each other. The change in each instance does not progress by discernible discrete steps. It is for this reason that the novel demonstratoraccording to this invention is of especial use in visually displaying the creation and collapse of areas of high magnetic flux intensity in the operation of electro-magnetic devices.

While the preferred illustrated embodiment of this invention is concerned with an induction type electric motor, it of course will be apparent to those skilled in this art that the broad basic principles of this invention may find application elsewhere in the demonstration of electrical phenomena without departure from the scope of this invention or of the claims subjoined to this specification.

Having thus described the present invention, what it is desired to secure by Letters Patent is:

1. A demonstrator for illustrating variations in magnetic fiux in an electromagnetic device comprising a supporting screen carrying indicla corresponding to elements of the device and having transparent areas corresponding to localities of the device wherein during operation magnetic flux plays; a first set of polarizers, arranged to intercept light rays vibrating in a common plane; and a second set of polarizers moving in correlated synchronism behind the first set of polarizers whereby the intensity of light transmitted through said first and second sets of polarizers is related to the intensity of magnetic flux of the corresponding elements of the device.

2. A demonstrator for illustrating variations in magnetic flux in an electromagnetic device comprising a supporting screen carrying indicia corresponding to elements of the device and having transparent areas corresponding to localities of the device wherein during operation magnetic flux plays; a first set of polarizers, arranged to intercept light rays vibrating in a common plane; a second set of polarizers, movably mounted behind the first set of polarizers; and means for moving the second set of polarizers in correlated synchronism whereby light transmitted through said first and second sets of polarizers is related to the intensity of magnetic flux of the corresponding elements of the device.

3. A demonstrator for illustrating variations in magnetic flux in an electromagnetic device comprising a supporting screen carrying indicia corresponding to elements of the device and having transparent areas corresponding to localities oi! the device wherein during operation magnetic flux plays; a first set of polarizers, arranged to intercept light rays vibrating in a common plane; a series of freely rotatable discs formed of light transmitting material mounted behind and upon said screen; means for causing motion of said discs in correlated synchronism; and a second set of polarizers mounted on said discs whereby the intensity of light transmlted through said first and second sets of polarizers is related to the intensity of magnetic flux in the corresponding elements of the device.

4. A demonstrator for illustrating variations in magnetic fiux in an electro-magnetic device comprising a supporting screen carrying indicia corresponding to elements of the device and having transparent areas corresponding to localities of the device wherein during operation magnetic flux plays; a first set of polarizers, arranged to intercept light rays vibrating in a common plane; a series of peripherally toothed freely rotatable discs formed of light transmitting material mounted behind and upon said screen; means for causing motion of said discs in correlated synchronism comprising toothed elements meshing with the teeth of said discs; and a second set of polarizers mounted on said discs whereby the intensity of light transmitted through said first and second sets of polarizers is related to the intensity of magnetic fiux in the corresponding elements of the device.

5. A demonstrator for illustrating variations in magnetic flux in an electromagnetic device, comprising a supporting screen, opaque indicia spaces opposite the transparent portion of the screen simulating windings of the pole pieces of the electromagnetic device, a first set of polarizers arranged to intercept light rays vibrating in a common plane, a series of freely rotatable discs formed of light transmitting material mounted behind and upon the screen, one of said discs opposite each of the opaque indicia spaces, means for causing motion of said discs in correlated synchronism, and a second set of polarizers mounted on said discs, whereby the intensity of light transmitted through said first and second set of polarizers is related to the intensity of magnetic fiux in the corresponding element of the electromagnetic device.

6. A demonstrator for illustrating variations in magnetic flux in an electromagnetic device, comprising a supporting screen, opaque indicia spaces opposite the transparent portion of the screen simulating windings oi the pole pieces of the electromagnetic device, a first set of polarizers arranged on the screen to intercept light rays vibrating in a common plane, a series of freely rotatable discs formed 01' light transmitting material mounted behind and upon the screen and leaving its central space between the same, a transparent disc mounted on the screen in said space and provided with a small opaque area, one of said first mentioned discs arranged opposite each of the opaque indicla spaces. means for causing motion of said discs in correlated synchronism, and a second set of polarizers mounted on said discs, whereby the intensity of light transmitted through said first and second sets of polarizers is related to the intensity of the magnetic fiux in the corresponding element of the electromagnetic device.

MARCACCIO. 

